Let's face it, Saber is already fully aware that Caster's not exactly the highest on the moral compass. Considering everything that's happened, they're not exactly likely to be buddy-buddy. She still remembers that time you made her stab Shirou, Caster. She still remembers that time you put her in a wedding dress, Caster.

Still, there's the running joke of Caster being obsessed with making Saber figurines, and cupid arrows are going around. I don't have thoughts or plans behind that but hey ill put it out there and maybe something can be planned out.